Examples of oily water separators of the plate type are described in U.S. Pat. Nos. 3,847,813 and 3,957,656. It will be seen that the basis of the separation resides in the provision of a plurality of corrugated separator plates mounted parallel to one another. The plates are sinusoidal or approximately so in cross section. The oil/water mixture is caused to flow between the parallel plates (which may be arranged in a parallel horizontal fashion as in U.S. Pat. No. 3,957,656 or in a somewhat inclined fashion as in U.S. Pat. No. 3,847,813), the effect of the sinusoidal path being alternatively to accelerate and to decelerate the fluid. These changes in velocity of the fluid which occur in directions both tangential to and normal to plate surfaces, combined with the inertial effects of differently sized oil droplets, tend to cause the droplets to coalesce. The coalesced oil droplets are suitably led off through weep holes in the crests of the corrugations.
The overall effect of the apparatus is that as the oil/water mixture progresses along the length of the separator, the oil gathers preferentially towards the top of the vessel. Oil is withdrawn from the top of the vessel at the end of the paths through the parallel plates and purified water from the bottom of the vessel.
A problem arises in aligning the plates with proper separation. The separation is all important since it is the varying separation normal to the direction of general flow which accounts in large part for the resulting coalescence. Alternative modes of interconnection between the parallel plates are described and illustrated in the two U.S. patents aforementioned. A further means of interconnection and separation which the assignees of the present inventor have used will be described below with reference to FIGS. 1 and 2 of the accompanying drawings. These prior proposed arrangements are not entirely satisfactory for the reasons which will be explained below with reference to FIGS. 1 and 2.